install: --offline does not fail on what is below a skipped optional dependency

docs/pm/cli/install.mdx

@@ -194,6 +194,8 @@ bun install --offline
 
 An install is only certain to cache the packages that it places in `node_modules`. To warm the cache for an `--offline` install, run an install on the same platform that places at least the same packages. An install with `--production` or `--omit` does not cache the groups it leaves out.
 
+`--offline` skips an optional dependency that is not cached, and anything below it that is not cached either. A package that an installed package requires is still an error.
+
 See [lockfile](/pm/lockfile) for more on `bun.lock`.
 
 ---

src/install/NetworkTask.rs

@@ -733,7 +733,7 @@ pub enum ForTarballError {
     OutOfMemory,
     #[error("InvalidURL")]
     InvalidURL,
-    /// `--offline` and the tarball is not in the cache. Already reported (once per
+    /// `--offline` and the tarball is not in the cache. Reported or recorded already (once per
     /// package); callers treat it like `AlreadyFailed`.
     #[error("TarballFailedToDownload")]
     Offline,

src/install/PackageInstaller.rs

@@ -1612,6 +1612,7 @@ impl<'a> PackageInstaller<'a> {
                         if package_manager::enqueue_git_for_checkout(
                             self.manager_mut(),
                             dependency_id,
+                            package_id,
                             alias.slice(string_buf!()),
                             resolution,
                             context,
@@ -1907,6 +1908,7 @@ impl<'a> PackageInstaller<'a> {
                     let is_duplicate = self.successfully_installed.is_set(package_id as usize);
                     self.summary.success += (!is_duplicate) as u32;
                     self.successfully_installed.set(package_id as usize);
+                    self.manager_mut().note_package_present(package_id);
 
                     if log_level.show_progress() {
                         self.node.complete_one();
@@ -2213,6 +2215,7 @@ impl<'a> PackageInstaller<'a> {
             }
 
             self.summary.skipped += 1;
+            self.manager_mut().note_package_present(package_id);
 
             if self.bins[package_id as usize].tag != bin::Tag::None {
                 self.trees[self.current_tree_id as usize]

src/install/PackageManager.rs

@@ -439,6 +439,9 @@ pub struct PackageManager {
     // `bun update <name>`: packages reachable from the workspaces in scope, see update_scope::plan_named.
     pub(crate) named_update_reachable: Option<bun_collections::DynamicBitSet>,
 
+    // --offline: what the install phase found; drained by enqueue::report_offline_misses.
+    pub(crate) offline_install: enqueue::OfflineInstall,
+
     // bun update: patched packages a move was held back for; drained by update_transitive::print_kept_patched.
     pub(crate) kept_patched: Vec<PackageID>,
     pub kept_patched_text: Vec<u8>,
@@ -2139,6 +2142,7 @@ pub fn init(
         wr!(updating_catalogs, Vec::new());
         wr!(update_target_workspaces, None);
         wr!(named_update_reachable, None);
+        wr!(offline_install, enqueue::OfflineInstall::default());
         wr!(kept_patched, Vec::new());
         wr!(kept_patched_text, Vec::new());
         wr!(dedupe_report, None);
@@ -2607,6 +2611,7 @@ fn init_with_runtime_once(
         wr!(updating_catalogs, Vec::new());
         wr!(update_target_workspaces, None);
         wr!(named_update_reachable, None);
+        wr!(offline_install, enqueue::OfflineInstall::default());
         wr!(kept_patched, Vec::new());
         wr!(kept_patched_text, Vec::new());
         wr!(dedupe_report, None);